Method and device for passing a web in connection with a finishing device of a paper or board machine

ABSTRACT

The invention relates to a method for passing a web (W) in connection with a finishing device of a paper or board machine, in which method the web (W) is passed from a preceding treatment stage to the finishing device in which the web (W) is finished in the finishing device and from which finishing device the web (W) is pased further to a subsequent treatment stage. The web (W) is brought to a roll ( 11; 14 ) of the finishing device as supported substantially before a nip area (N 1 ; N 2 ). The web (W) is passed from the circumference of a roll ( 12; 15 ) of the finishing device as substantially supported after the nip area (N 1 ; N 2 ). The invention also relates to a device for passing a web in connection with a finishing device of a paper machine. The web (W) can be brought by means of the device to the circumference of a roll ( 11; 14 ) of the finishing device substantially before a nip area (N 1 ; N 2 ) and/or the web (W) can be passed from the circumference of a roll ( 12; 15 ) of the finishing device substantially after the nip area (N 1 ; N 2 ).

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This application is a U.S. national stage application ofInternational Application No. PCT/FI01/01008, filed Nov. 21, 2001, andclaims priority on Finnish Application No. 20002550, filed Nov. 21,2000, the disclosure of each application being hereby incorporated byreference herein.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

[0002] Not applicable.

BACKGROUND OF THE INVENTION

[0003] As known in the state of the art, free draws have been used inpaper machines when passing a paper web from one treatment stage to thenext. The general trend today is that attempts are being made to passthe paper web as supported from one treatment stage to the next, and thedevelopment has indeed moved forward so that the wet end and the dryersection of the paper machine have for the most part been provided withmeans so that the transfer of paper is supported over the entiredistance. However, in finishing there are stages in which unsupportedruns of the web are still used at present, for example, in connectionwith calenders or on-line coating devices. Since the current trend isalso that finishing devices are connected as on-line units to the papermachine, the significance of web support matters for the efficiency ofthe total line is greater than before when using off-line furthertreatment units. Since all unit process devices are in the same chain,the problems presented by free draws in the transfer of the web andpossible web breaks cause problems to the entire line and may cause evena shutdown of the entire line.

[0004] Today's paper machines also aim at an increase of speed anddecrease of the basis weight of the paper web as well as at higherefficiency requirements. Thus, unsupported runs cause problems, andtherefore their elimination is very important.

[0005] Thus, it is an object of the invention to provide a method and adevice in connection with which the run of the web is supported inconnection with a finishing device.

[0006] With respect to the state of the art associated with theinvention, reference is made to FI patent application 973725 whichdiscloses an arrangement in which a web is conveyed by means of asupport wire or equivalent to a multi-nip calender from the last dryingcylinders placed substantially higher than the other cylinders of adryer section, on which support wire the web is passed to the firstpre-nip of the calender formed between the topmost calender roll and abelt calender roll or a wire guide roll.

[0007] An arrangement is known from the state of the art in which apaper web is passed as a supported run through a calender supported by asupport member which has been guided to run through a calendering nip ofthe calender. In this respect, reference is made to FI patent 95 061. Aproblem in this prior-art arrangement is that the support member ofpaper influences the process itself and thus also the quality of thepaper being manufactured as the support member runs through the nip.Further, this restricts the selection of the support member material tobe used because the support member thus takes part in the process, whichmeans that the material of the support member shall be selectedaccording to the demands of the process and the process parameters shallbe adjusted taking account of the effect of the support member.

SUMMARY OF THE INVENTION

[0008] It is thus a particular object of the invention to provide afully supported run of the paper web in connection with a finishingdevice, which does not affect the manufacturing process itself, nor thequality of the paper that is manufactured.

[0009] In accordance with the invention, a web, in particular a paper orboard web, is brought to the circumference of a roll in a finishingdevice as supported substantially before the nip area and the paper webleaves the circumference of the roll of the finishing device and ispassed to be supported by means of a support member substantially afterthe nip area. In accordance with the invention, the paper web is broughtto the finishing device while supported by a support member, forexample, a belt, a felt or a wire or equivalent such that the transferis supported over the entire distance from a preceding treatment stageto said finishing stage, during it and after it further to the followingtreatment stage after it.

[0010] In accordance with the invention, a support member loop is usedin connection with which two or more rolls have been arranged to guideit, and onto which support member a paper web is passed and on supportof which support member the paper web is conveyed into connection with aroll of a finishing device substantially before the nip of the finishingdevice and, in a corresponding manner, the web is passed by means of asupport member loop from a roll of the finishing device to furthertreatment. The support member runs past the roll substantiallytangentially to the roll of the finishing device.

[0011] The invention is particularly suitable for use in connection withcalenders, in particular soft calenders, in which connection it alsoprovides the advantage that, when the support member is placed such thatthe paper web to be calendered is guided to run on the circumference ofa thermo roll before a nip, the paper web and also the support memberfor its part form a shield which prevents the heat of the thermo rollfrom evaporating into the surroundings, with the result that the heat ofthe thermo roll is transmitted to the paper. By this means, the web canbe passed to the nip while it is hot and the heat of the thermo roll canbe utilised with a greater efficiency than in the arrangements knownfrom the state of the art.

[0012] The apparatus in accordance with the invention has been placed inconnection with a finishing device and the process stage preceding it isconstituted by, for example, a dryer section or a coating unit and it isfollowed by, for example, a reeling or coating unit and, in accordancewith the invention, the web runs from the preceding process stage to thesubsequent process stage through the process stage in question assupported all the time by means of support members and the rolls used inthe process stages.

[0013] The support member according to the invention is formed of aloop-shaped support member which is guided by two or more rolls, and oneor more support member units have been arranged in connection with afinishing device to support the web.

[0014] When, in accordance with the invention, the run of the web hasbeen provided as supported in connection with a finishing device, it ispossible to raise the speed of the paper machine and use paper gradeshaving a lower basis weight. Thereby, a greater efficiency is achievedon the paper machine. A supported run is not so susceptible to webbreaks and other disturbances, whereby substantial benefits are achievedin the entire on-line process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the following, the invention will be described in more detailwith reference to the figures of the accompanying drawing, to thedetails of which the invention is, however, not by any means meant to benarrowly confined.

[0016]FIG. 1 is a schematic view of one application of the invention inconnection with a two-nip soft calender.

[0017]FIG. 2 is a schematic view of one application of the invention inconnection with a one-nip soft calender.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] As shown in FIG. 1, a paper web W is brought by a support member10 to a Sym-roll 11 of a soft calender, from which it is passed alongthe roll 11 into a calendering nip N1 and further from the surface of athermo roll 12 by means of a support member 13 to a Sym-roll 14 of asubsequent calendering nip N2 and further to a thermo roll 15, fromwhich it is passed by means of a support member 16 to further treatment,for example, to a reel-up. Thus, a loop-shaped support member 13 hasalso been disposed in connection with the run between the calenderingnips N1, N2, on which support member the web W is passed as supportedfrom, for example, a thermo roll of the calendering nip N1 to, forexample, a Sym-roll of the following nip N2.

[0019] As shown in FIG. 2, a paper web W is passed from a dryer section40 of a paper machine to a support belt 20, by means of which said web Wis transported to a thermo roll 21 of a calender and passed along itssurface to a calendering nip N3 and further along the surface of aSym-roll 22 to a second support belt 23, which has been placed above thepaper web W and in connection with which, for example, blow suctionboxes 24, 25 have been arranged to support the run of the web W. Afterthat, the web W is passed by means of a roll 26 to further treatment.

[0020] As shown in FIGS. 1 and 2, a support member unit 30 comprises asupport member 10, 13, 16, 20, 23, for example, a belt, a wire, a feltor equivalent, which has been arranged to run in a loop-like fashionwhile guided by guide rolls 33. Depending on the application, two ormore guide/alignment rolls 33 have been arranged in connection with eachsupport member 10, 13, 16, 20, 23.

[0021] As illustrated in FIGS. 1 and 2, the paper web W is passed to thecalender substantially before the calendering nip N1; N2; N3 by means ofthe support member 10; 13; 20 and the web W is passed away from a rollof the calender substantially after the nip N1; N2; N3 and passed tofurther treatment by means of the support member 13; 16; 23. It shall beparticularly noted that the support member does not take part in theprocess because it does not run through the calendering nip N1, N2, N3,but, instead, the support member brings the web W substantially close tothe nip to the circumference of the roll defining the nip and, in acorresponding manner, the support member receives the web substantiallyafter the nip from the circumference of the roll defining the nip.

[0022] Above, the invention has been described with reference to onlysome of its advantageous application examples, to the details of whichthe invention is by no means meant to be narrowly confined.

1. A method for passing a web (W) in connection with a finishing deviceof a paper or board machine, in which method the web (W) is passed froma preceding treatment stage to the finishing device in which the web (W)is finished in the finishing device and from which finishing device theweb (W) is passed further to a subsequent treatment stage, characterisedin that the web (W) is brought to a roll (11; 14; 21) of the finishingdevice as supported substantially before a nip area (N1; N2; N3) andthat the web (W) is passed from the circumference of a roll (12; 15; 22)of the finishing device as substantially supported after the nip area(N1; N2; N3), and that the method is applied in connection withcalenders, in particular soft calenders.
 2. A method according to claim1, characterised in that the web (W) is passed as supported by a supportmember (13) between the treatment stages of the finishing device.
 3. Amethod according to claim 1 or 2, characterised in that the web (W) issupported by a support member loop (10; 13; 16; 20; 23), the run ofwhich is guided by two or more rolls (33).
 4. A method according toclaim 1, characterised in that the support member (10; 13; 16; 20; 23)runs past the roll (11, 12, 14, 15, 21, 22) tangentially to the roll(11, 12, 14, 15, 21, 22) of the finishing device.
 5. A method accordingto claim 1, characterised in that the web (W) is passed to a thermo roll(21) of the calender such that the web (W) is guided to run on thecircumference of the thermo roll (21) before a nip (N3) such that theweb (W) forms a shield which prevents the heat of the thermo roll fromevaporating into the surroundings.
 6. A device for passing a web inconnection with a finishing device of a paper machine, characterised inthat the web (W) can be brought by means of the device to thecircumference of a roll (11; 14; 21) of the finishing devicesubstantially before a nip area (N1; N2; N3) and/or the web (W) can bepassed from the circumference of a roll (12; 15; 22) of the finishingdevice substantially after the nip area (N1; N2; N3), and that thedevice has been arranged to be used in connection with a calender, inparticular a soft calender.
 7. A device according to claim 6,characterised in that the device has been formed of a support memberloop (10, 13, 16, 20, 23) having two or more rolls (33) disposed inconnection with it in order to guide it.
 8. A device according to claim6 or 7, characterised in that the support member (10, 13, 16, 20, 23) ofthe device has been arranged to run past the roll substantiallytangentially to the roll of the finishing device.
 9. A device accordingto any one of claims 6 to 8, characterised in that one or more supportmember units have been arranged in connection with the finishing device.